Risk Assessment And Prevention Of Coal Mining Support Crushing Under Unconsolidated Confined Aquifer

In China, North China, Northwest, Huainan, Huaibei mining area is by improving mining upper limit, mining under thin bedrock coal, but because reducing coal pillars, study on strata behavior regularity of the working-face with thin coal seam and stiff roof is insufficient, mining support crushing、mine flooding、and quicksand frequently occur. In this paper, Panxie coal mine two working face as the background of raising the upper limit of mining, measure the mine pressure regularity of working face, and then using the numerical simulation software, Respectively, the lifting surface mining technology conditions and working surface geological parameters of finishing and inserting synthetical index method of the pressure frame risk evaluation, At last, the prevention and cure suggestion.(1)Influence of Panji second coal mine 12226 working face overburden movement by the coal pillar, affected by coal pillar of 8 coal, the pressure in the upper part and middle part of the working face is increasing, consistent with mining practice; The roof of the maximum pressure and stress concentration occurred in the coal column below, The vertical stress appears peak value in the coal body side of the coal pillar on the working face.(2) The relationship between the hydraulic support selection and the thickness of the base rock:the 50m-60m thick bedrock corresponding bracket for the 5600kN rated working resistance; the 40m thick bedrock corresponding bracket for the 6400kN rated working resistance; the 30m thick bedrock corresponding bracket for the 8600kN rated working resistance; the bedrock of its thickness is 20m, support needs to be increased to 10800kN working resistance, to effectively control the roof sinking.(3)Mining height control in less than 4.8m, reduce the generation of overlying rock fissure zone, to prevent water inrush; coal seam dip angle is bigger, under crossheading the thickness of bedrock is increasing, working face in the lower part of the roof subsidence is small, is conducive to raise safety mining.(4)The mining working face is 120m, select the hydraulic support of moderate intensity (6400KN). Increase the working face to 150m, must use strength of hydraulic support 12800KN, can effectively control the roof subsidence, to avoid the occurrence of support crushing accident.(5)By filling method is better than all caving goaf method effectively control the stope roof subsidence, normally without support crushing accident, the latter lead to support crushing risk easily.(6) The comprehensive index method to classify the four levels of the index W, to measure the increase of the upper limit of the working surface of the support crushing coefficient. When W<0.3, no support crushing hazards, the effective control of the top bracket, reasonable selection; when 0.3≤W<0.6, third dangerous support crushing, appropriate to increase the effective support of roof control; when 0.6≤W<0.8, second dangerous support crushing, you need to relayout of working face; when W is larger than 0.80, first dangerous support crushing, you should stop, rear quasi production safety improvement.